What did dmitri mendeleev discover in 1869

Dmitri Mendeleev created the Periodic Table in the year 1869. I hope I helped! :)

In 1869, just five years after John Newlands put forward his Law of Octaves, a Russian chemist called Dmitri Mendeleev published a periodic table. Mendeleev also arranged the elements known at the time in order of relative atomic mass, but he did some other things that made his table much more successful. I hoped that I helped you alot; but keep going further to complete your assignments and Graduate High School or Middle School.